Aortic Aneurysm Size and Graft Behavior After Endovascular Stent-Grafting: Clinical Experiences and Observations Over 3 Years

Past, Present, and Future Endograft Devices

Since the original descriptions of endovascular grafts for treatment of aneurysms, a number of devices and approaches have been developed. The following is a discussion summarizing the number of devices which have been developed and used in patients, as well as chosen the directions of this technology. The diversity of approach from an engineering and materials point of view speaks of the fact that opportunity exists for continued development in the future.

Endovascular treatment of aneurysmal disease

Endovascular repair of abdominal aortic aneurysm using stent grafts that are delivered intraluminally by catheters is a less invasive alternative to open surgical repair. Endovascular surgery has been studied for over a decade, and early results are comparable to open repair. With extended follow-up care, however, postoperative complications and graft failures have been reported in some patients, resulting in reintervention, conversion to open repair, and death. The high incidence of secondary interventions causes some researchers to question the durability of endograft repair and emphasizes the need for detailed long-term follow-up care. This article describes the evolution of endovascular treatment of abdominal aortic aneurysm from its origin to its current state and discusses the future direction of endovascular therapy.

Imaging of aortic stent-grafts and endoleaks

Although the technical success of stent-graft implantation is established and relatively safe, data on the long-term safety and efficacy of endovascular repair are just emerging. Because several late complications of aortic stent-graft placement have been observed, life-long follow-up remains essential. Imaging methods form an integral part of every stage of endovascular aortic aneurysm repair. The current imaging strategy should include initial plain films, CT angiography, and color-coded Duplex sonography. Plain films are an excellent means to detect migration, angulation, kinking, and structural changes of the stent mesh, including material fatigue, at follow-up. Helical CT angiography is considered a potentially revolutionary method for the noninvasive complete postprocedural assessment of aortic sten-grafting. Current data justify the use of biphasic C angiography as the postprocedural imaging technique of choice in most patients [118]. Ultrasound offers the advantages of low cost and lack of radiation exposure. High-quality ultrasound reliably excludes endoleaks in patients after stent-grafting of AAAs. There is a substantial variability, however, in measuring the diameter of aneurysm sacs; thus, confirmation using an alternative study is prudent in cases that demonstrate a significant change in size during follow-up. MR angiography serves as an attractive alternative to CT angiography in patients with impaired renal function or known allergic reaction to iodinated contrast media. With current techniques, the visualization of aortic stent-grafts (with the exception of stainless-steel-based devices) is sufficient with MR angiography. There is evidence that MR imaging is superior to CT angiography in detecting small type 2 endoleaks or for excluding retrograde perfusion in patients with suspected endotension. The role of diagnostic catheter angiography is limited to assessment of vascular pathways in equivocal cases or for suspected endotension. Currently, a consensus view about postprocedural management after aortic stent-graft implantation is lacking. The authors propose performing a baseline CT angiography at discharge and a biphasic CT angiography and Duplex ultrasound scan at three months. In patients with no evidence of an endoleak, CT angiography, plain film and Duplex sonography (abdomen) should be repeated every year after endovascular repair. If an endoleak is present at follow-up, immediate appropriate treatment should be initiated.

Imaging of abdominal aortic aneurysm before and after endoluminal stent-graft repair

Imaging is an essential component of endoluminal aneurysm repair. Detailed imaging with computed tomography, magnetic resonance imaging and angiography, alone or in combination, is required for the initial assessment and planning. Careful, lifelong follow-up is essential since complications of endoluminal repair may take months or years to appear. Follow-up imaging requires a combination of plain film radiography, colour Doppler ultrasound and helical computed tomography. Magnetic resonance imaging may be valuable for the follow-up of non ferro-magnetic endografts and intra-arterial angiography will be required for specific cases.